Squib driver circuits provide regulated currents in order to ignite the squib and deploy the airbag for passenger safety. The squib is a pyrotechnic element which ignites when a certain amount of energy is provided. In FIG. 1, an example of a typical squib driver circuit 100 can be seen. This driver circuit 100 is generally an integrated circuit or (IC) having an on chip high side power MOSFET Q1 and a low side power MOSFET Q2 that are respectively driven by drivers 102-1 and 102-2. The squib 104 is coupled between two pins Zx and ZMx that pin VZx (which is typically coupled to a power supply) can provide a current (through the high side power MOSFET Q1 and pin Zx) to the squib 104. Squib 104 is then coupled to ground through pin ZMx and the low side power MOSFET Q2. A generally constant current pulse for a time Δt is required in order to ignite the squib 102, and the energy in the squib can be calculated as follows:Energy≈1^2*R*Δt  (1)
The amount of energy indicated in equation (1) is provided to the squib 104 by activating the high side power MOSFET Q1 and the low side power MOSFET Q2 at the same time. However, it is undesirable ignited the squib 104 by or in response to any fault condition (i.e., a short from battery 106 as shown the example of FIG. 2).
Turning now to FIG. 3, a conventional squib driving circuit 300 (which is typically an IC) that is configured to limit the current in the powered and unpowered states. Current limiting is generally achieved by comparing the voltage across a sense resistor R2 with a reference voltage generated by a reference resistor R1 and a current source 312. The current limit Ilimit is then given by the following equation:
                              I          limit                ≈                              (                                          R                1                                            R                2                                      )                    *                      I            ref                                              (        2        )            The current limiter 304 performs the current limiting as long as there is enough power for amplifier 310. When the current through the squib 104 exceeds that the current limit Ilimit the amplifier 310 deactivates or turns off transistor Q3. Additionally, there is a surge current controller 302 (which uses fault mode sensing circuitry 308 and surge current limiter 306 that generally ensures that the transistor Q3 is turned off quickly to limit the energy in the squib 104). Node V0, however, is a high impedance node, which makes it rather difficult to achieve stable operation, in particular for the typically wide range of resistive, inductive or capacitive loads. In order to stabilize the IC 300, the pole-zero compensation network including resistors RZ and RZ1 and capacitors CC and CC1 at the output of the amplifier 310 becomes more complex and requires more area. This increases the total costs of IC 300, while the potential instability remains an issue. If the RLC-network of the squib 104 (i.e., resistor RS, capacitor CS, and inductor LS) provides only weak damping (i.e., R<1Ω, L>70 μH and C<10 nF) large signal current oscillations may occur. This results in an unstable behavior of the circuit. Furthermore, if the current limiter 304 (including the amplifier 310) does not operate (due to an unpowered state) the Miller capacitance between gate and drain of the transistor Q3 may not be discharged when pin Zx is shorted to the battery (i.e., 106), which an undesirably deploy the squib 104.